Synthetic organic routes to precisely defined conjugated
macromolecules (molecular scale wires) will be described using
solution and solid phase approaches. The molecular scale wires
are based on poly(phenylene ethynylene)s and poly(thiophene
ethynylene)s and they possess thiol end groups to function as
molecular scale alligator clips. Ordering of these molecular
scale wires on gold surfaces has been studied by ellipsometry,
XPS, and grazing angle IR. Experimental approaches will be
described for isolating some of these single molecules in alkane
thiolate self-assembled monolayers and addressing them with an
STM probe. Single molecule conductance has been measured using a
mechanically controllable break junction. These experiments
demonstrate single molecule conductivity and they are a prelude
to the testing of molecular scale devices. Some potential
molecular scale structures that have been synthesized are wires
with tunnel barriers, wires with quantum wells, three terminal
systems which could act as transistors, and four terminal systems
that can be actual logic devices. Scenarios will be outlined
wherein a single molecule could function as a logic device rather
than the traditional use of multiple transistors. The enormous
potential and obstacles of molecular scale electronic
architectures will be discussed.